MSU Physicist Develops New Model for Speed and Motion Solar Flares

A solar flare is a sudden flash of brightness observed near the Sun’s surface. It involves a very broad spectrum of emissions, requiring an energy release of typically 1×1020 joules of energy. They can emit up to 1×1025 joules. Flares are often, but not always, accompanied by a coronal mass ejection (CME). (A Coronal Mass ejection (CME) is an unusually large release of plasma from the solar corona. They often follow solar flares and are always present during a solar filament eruption. The plasma is released into the solar wind, and can be observed in coronagraph imagery).

The flare ejects clouds of electrons, ions, and atoms through the corona of the sun into space. These clouds typically reach Earth a day or two after the event. X-rays and UV radiation emitted by solar flares can affect Earth’s ionosphere and disrupt long-range radio communications. Direct radio emission at decametric wavelengths may disturb the operation of radars and other devices that use those frequencies. The term is also used to refer to similar phenomena in other stars, where the term stellar flare applies.

Solar flares affect all layers of the solar atmosphere when the plasma medium is heated to tens of millions of Kelvin. The layers of solar atmosphere are photosphere, chromosphere and corona. It is done while the cosmic-ray-like electrons, protons, and heavier ions are accelerated to near the speed of light. They produce radiation across the electromagnetic spectrum at all wavelengths.

Generally, flares occur in active regions around sunspots, where intense magnetic fields penetrate the photosphere to link the corona to the solar interior. Flares are powered by the sudden release of magnetic energy stored in the corona. The same energy releases may produce coronal mass ejections (CME) although the relation between CMEs and flares is still not well established.

A Scientist from Montana State University (MSU) has developed a new model that can expose an outcome in advance of solar plasma during solar flares. It is similar to the way traveled by thrown baseball.

Sean Brannon, a postdoctoral researcher in the MSU Department of Physics within the College of Letters and Science, present his model at the Solar Physics Division of the American Astronomical Society conference in Boulder, Colorado.

He demonstrated a model that may tell, how solar flares are developed and can provide better ways to conclude them. This model can have applications in power protecting grids, communication technology, and aeronautics from the energy released by the flares.

He used data from the NASA Interface Region Imaging Spectrograph Satellite (IRIS) to detect transition region (specific layer of sun). The transition region is thin and complex. It separates the corona (sun’s outermost layer) from the chromosphere (sun’s inner layer). These three factors (transition region, corona and chromosphere) are the reason for interest and mystery to scientists.

Temperatures in the corona can reach several million degrees, Kelvin, up to a factor of 100 than any other layer of sun’s atmosphere.

A solar flare curve through the corona can be up to 10 million degrees, Kelvin. This is confusing and seems unreasonable since the corona is the next layer from the sun. Hence, it should tenably be the coolest.

The Spectrograms of IRIS are made by the process similar to when light passes through prism and breaks into different colors. Each color is built up by a different kind of atom in the solar atmosphere. We can extract all kinds of interesting information about what the plasma is doing based on that spectrum.

Brannon said, “For example, if the light is more red or blue than we have expected, then we know that the plasma is moving either away from or toward us.”

To look at the process of sun’s solar flare, Brannon used IRIS’s data. During a solar flare, plasma from the sun can heat more than millions of degrees Kelvin and vaporize into the corona. There it fills or is carried into powerful magnetic fields that give it a curvical, loop-like shape.

Brannon said, “We then expect that this hot plasma will cool off over the next several minutes to hours. As it cools, models predict that it should start to drain back out of the loops, resulting in spectral signatures that should be detectable.”

“Up until now, however, there haven’t been any published papers analyzing an observation of the entire filling, cooling, and draining process, nor have there been any papers that attempt to model a spectral observation as a signature of the draining. The cooling and draining are important to look at since we’d like to be sure that the plasma we’re measuring is evaporated plasma draining back, and not some other source of plasma”, he continued.

For describing the speed at which a spot of plasma falls from the top of an oval-shaped flare loop and how it looks on an IRIS spectrograph. The outcome indicates that plasma is draining from the loops at free-fall speeds. The location and timing of the draining plasma match that which was observed vaporizing.

The forecasting of large solar flares is essential due to their emitting of very large amounts of energy that can disorganize power grids, satellites, communication technology and aeronautics.

Brannon said, “The sun really dominates Earth’s environment, climate, and space in which Earth lives. What the sun does can have very profound impacts on life here on Earth. So, understanding the sun’s processes can help us determine how to protect technology and people.”

Dana Longcope, MSU Physics Professor and Brannon’s academic adviser and is national chairman of the Solar Physics Division, said, ” while solar flares are unpredictable making it difficult to find one to observe, Brannon was able to identify a specific IRIS observation, enabling him to make his analysis.”

He then said, “He came up with a very different interpretation of what happens during a solar flare. It is one of the most compelling quantitative observations I’ve seen as to what we’d expect to see during a solar flare. It’s a credit to a scientist when they look at the data and they aren’t blinded by what they expect to see, but rather keep an open mind and observe what is actually happening.”